This application relates to a lockably adjustable hinge. More particularly, this invention concerns such a hinge useable between a back and seat part of a seat for a vehicle.
It is conventional to provide bucket seats in the front sitting places of an automotive vehicle whose back parts and seat parts are hinged relative to one another about a horizontal axis. Means is provided for locking the back relative to the seat in any of a plurality of angularly offset positions. Thus the passenger or driver may adjust the inclination of his seat back for the position most comfortable to him or her.
It has been suggested in German Pat. No. 1,150,586 to provide a plurality of angularly equispaced axially extending teeth on one of the hinge elements centered on the hinge pintle and another such array on the other hinge element. Means is provided, usually operable by means of a screw-type adjustment knob, to displace these two arrays into and out of a mesh with each other. When meshed they lock the two elements, and therefore the seat part and back part of the seat, relative to one another. When out of mesh the back can be pivoted relative to the seat into the desired position where it can be tightened up and locked in place. The disadvantage of this system that the back part must be completely unloaded in order to allow the hinge lock to be unfastened and the seat to be swivelled. This makes it difficult for a person to find other than by a trial-and-error process the position that suits him or her best.
Another arrangement described in German Offenlegungsschrift No. 2,138,972 forms each of the hinge elements with a respective annular array of angularly equispaced holes. These arrays are centered on the pintle axis and axially in line, but the angular spacing of the holes of one array is different from that of the other array so that pins can be fitted through two aligned holes in just about any position of the back relative to the seat. Such an arrangement suffers from the same disadvantages of the arrangement described immediately above, and mainly that the seat back must be completely unloaded for the user to adjust it.
In German Pat. No. 1,297,496 an arrangement is described wherein one of the hinge elements of the seat is formed with an internal gear and the other element is formed with an external gear mounted on an eccentric pin and meshable with the internal gear. Rotation of the eccentric pin causes the external gear to travel around within the internal gear and, therefore, change the relative positions of the two elements. In such a system it is necessary to provide extremely robust and hard-to-operate arresting means for this external gear. Even so the adjustment obtained is relative coarse.
Finally, it has been suggested in German Pat. No. 1,291,570 to provide on each of the hinge elements a respective internal gear centered on the pintle axis. These two gears are of different diameters and respective external gears carried on a common eccentric shaft mesh with them so that rotation of these shafts will angularly offset the two hinge elements. This system, although it allows for a fine adjustment of the seat while loaded, is relatively complicated, and, therefore, expensive. At the same time it needs separate and heavy-duty locking means to prevent rotation of the external gears once the desired position is set.